We are testing the effects of semipurified cholesterol-free diets in Vervet monkeys. These diets cause hyperlipemia and aortic sudanophilia in this species. We have completed an experiment examining the effects of 3 or 6% elaidic acid in the diet and one in which the effects of native and randomized peanut oil were compared. Work up of tissue samples is in progress. One current experiment involves investigation of the effect of 0.1% cholesterol when added to a diet in which the carbohydrate (40%) is lactose. In another study the effects of diets containing casein and soy protein are compared with diets in which the arginine/lysine ratios of these two proteins are manipulated by adding arginine to casein and lysine to soy protein.